@AHorneffer Great work figuring this out. I have compiled the Git head with your changes and it does indeed fix the issue with the Gerber output. I do get an error when I open the gerber files in Gerbv where it states that the hole diameter is not set in the drill file but all the holes appear to be the correct size so it does not look to be a major concern. EDIT: it turns out Gerbv is actually seeing something in the mask layers it thinks should be holes and complaining that the diameter is not set. It has nothing to do with the drill file.
I will comment on the Github issue that this does seem to fix current Gerber output issue. We can only hope there is still someone with commit access and a desire to continue working on Fritzing listening.
The Gerber output is instantaneous now and the ground fill generation is really clean.
If anyone would like to try it our I have built an actual release version for 64bit Linux. Here is a link to a copy on a free file transfer site. https://we.tl/bEcjUwZLZr I do not know how long it will be available. If it does not work just PM me your Email address and I will send it over. NOTE: It is almost 50Mb.